1. Field of the Invention
The present invention relates to a torsional damper type flywheel device divided into two masses coupled to each other via a torsional spring.
2. Description of the Related Art
A prior art torsional damper type flywheel device is disclosed in, for example, Japanese Utility Model Publication SHO 63-42950. The flywheel device, as illustrated in FIGS. 8 (Prior Art) and 9 (Prior Art), includes a drive side flywheel 10', a driven side flywheel 20' rotatable relative to the drive side flywheel 10', a K spring mechanism 30' directly connected between the drive side and driven side flywheels, a K1 spring mechanism disposed parallel to the K spring mechanism, and a friction mechanism disposed in series with the K1 spring mechanism so that the series combination of the K1 spring and the friction mechanism is connected between the drive side and driven side flywheels.
The drive side flywheel 10' includes an outer ring 12', an inner ring 14' disposed radially inside outer ring 12', an engine side drive plate 16' and a clutch side drive plate 18'. The drive plates 16' and 18' are fastened to the outer ring 12' by a plurality of rivets 15'. The drive plates 16' and 18' are constructed of steel for the purpose of increasing the structural reliability and reducing an axial length of the flywheel device. The inner ring 14' and engine side drive plate 16' are fastened to an engine crankshaft by a plurality of bolts. Windows 17' and 19' for supporting the K and K1 spring mechanisms therein are formed in the engine side drive plate 16' and clutch side drive plate 18', respectively.
However, as seen from FIG. 8 (Prior Art), the inertial mass of the assembly of the drive side flywheel 10' and the spring mechanisms is axially spaced from a surface S' of the flywheel device contacting the engine crankshaft by a distance a'. As a result, when the flywheel device is rotated at high speeds and a centrifugal force F' arts on a center of the inertial mass of the assembly of the drive side flywheel 10' and the spring mechanisms, a moment M' (M' =F' * a') causes the drive side flywheel 10' to axially incline toward the engine crankshaft side, because the engine side drive plate 16' is constructed of a thin steel plate and can easily be deformed.